Riveted sheet metal belt fasteners, whether of the plate or hinge forms, are typically produced as a strip of connected multiples divisible into five-rivet fasteners, which, as shown by Pat. Nos. 4,620,657 and 4,688,711, lend themselves to the gang-driving of all of the rivets of a given fastener section simultaneously. This is accomplished by the use of a multi-pronged driver whose multiple drive rods are insertable into a guide block forming part of a fixture in which the end of a belt, the unclenched fastener, and the rivets which will secure the fastener to the belt, are positioned for assembly by the driving and setting of the rivets.
The guide block is formed with multiple through holes which receive and position the rivets to enter the countersunk holes in the upper plate of the fastener section, and which guide the multiple drive rods of the multi-pronged driver to impact the rivet heads when the cap or head of the multi-pronged driver is in turn struck by a hand-held hammer, or by a power tool capable of delivering an impact to the driver head.
Driving and setting multiple rivets with a hand-held hammer requires strength and skill to deliver a square blow to the driver head, i.e., one which is centered upon the driver head without also exerting a side thrust tending to distribute unequally the force transmitted to the rivets being driven or set. Failure to strike squarely, a not infrequent occurrence in the driving and setting of the many rivets required across conveyor belts 24 to 48 inches in width, increases the number of blows required to drive and set the rivets, and stresses the driver head undesirably, shortening its life. The use of hand-guided power hammers to relieve the maintenance man of the physical burden of wielding a heavy, hand-held hammer is subject to the same alignment problems, all of which tend to increase the downtime of conveyors in use when belt breakages occur, as, for example, in underground mining, where belt repair must often be made under trying circumstances.
Attempts to improve the power-driving and setting of rivets for this service have thus far focussed upon the power-driving of each rivet singly, using a commercial bulk nailing gun for the purpose, as shown by U.S. Pat. No. 4,440,336. In the arrangement there shown, the nailing gun is secured to an arm hinged for vertical swinging movement on a carriage movable transversely of the belt to which the fastener is to be attached, the carriage being guided by ways secured to the upper surface of a bar clamp which secures the belt in the riveting fixture. An elongated gauge plate perforated with a hole pattern matching that of the belt fastener is positioned beneath the mounting arm of the gun, which is provided with a downwardly-extending feeler pin to find the holes in the perforated plate to position the gun to drive each nail-pointed rivet singly through the perforated plates of the belt fastener, and the belt in between, in a single discharge of the gun. The gun is then lifted, moved laterally to position the feeler pin in the next hole of the row, and the operation repeated. When one row of rivets has been driven, the swing arm of the gun is indexed on the carriage to align the feeler pin with the next row of holes in the perforated gauge plate for the driving of the next row of rivets, and again for the next row.
The elaborate and cumbersome fixturing required to position the gun in turn over each perforation of the fastener plate reflects the danger to personnel of the bouncing, deflected rivet that misses the hole. It appears to lack the flexibility needed for field repair of conveyor belts in situ, and is manifestly unable to drive multiple self-setting rivets simultaneously.
It is accordingly the object of this invention to improve the technique of gang-riveting in the stated context by the use of a hand-held power tool especially adapted for the simultaneous driving and setting of multiple nail-rivets.